The idea is, if we can modulate the rate at which nuclear reactions take place (Fusion/Fission), can we create and modulate gravitational ripples in space time, more or less in the same was as we do with AM radio?

This question appears to be off-topic. The users who voted to close gave this specific reason:

"This question is about other space sciences (physics, weather, astronomy, etc), and does not directly pertain to space exploration as outlined in the help center." – Jack, uhoh, kim holder, Nathan Tuggy, Organic Marble

$\begingroup$Interesting question! I think this would be a better match for Physics SE$\endgroup$
– JackJun 20 '18 at 15:03

$\begingroup$I think the answer is no. If I understand correctly, a charged battery has a larger mass than a discharged battery by exactly Δm = ΔE/c^2. So if you turned nuclear mass (from a reactor) into energy in the form of flowing electricity or light, and then stored it as chemical energy in a battery, the total mass of the system doesn't change. But you should probably ask this in Physics SE instead.$\endgroup$
– uhohJun 20 '18 at 15:11

1

$\begingroup$@uhoh: While this is true, simply moving large mass-equivalents of energy from one end of a large system to another at the speed of electrons could reasonably be expected to cause some gravitational waves. (Almost certainly far too small to be of the slightest use to any detectors we are capable of building now or in the future, but that's for Physics to say for sure.)$\endgroup$
– Nathan TuggyJun 20 '18 at 15:36

$\begingroup$Nuclear reactors are 100's of megawatts or more, so that would be the energy per second that you should convert to mass per second by dividing by c^2. It's still tiny, but without question the rate of change of the mass of the nuclear fuel would be modulated by the power output modulation, and this would make quite minuscule but non-zero gravitational waves. "zero known effect" is probably not a correct statement, though "practically zero" or "probably immeasurable" might work.$\endgroup$
– uhohJun 20 '18 at 16:27

$\begingroup$@uhoh Right. I think the post wants to know some tricky nuclear-gravitational coupling and not for a purely GR idea.$\endgroup$
– peterhJun 20 '18 at 18:02

$\begingroup$I think the post is just asking about making mass "go away quickly" by changing it to energy. But a higher level answer is also interesting.$\endgroup$
– uhohJun 20 '18 at 18:09

$\begingroup$Thank you all! A good starting point. The question was put on hold as it was marked off topic for here with the recommendation to post in PhysicsSE, so I will head over there!$\endgroup$
– DennisonJun 20 '18 at 21:28